##
# NOTE:
# We'll move this class to Clusters::Platforms::Kubernetes, which contains exactly the same logic.
# After we've migrated data, we'll remove KubernetesService. This would happen in a few months.
# If you're modyfiyng this class, please note that you should update the same change in Clusters::Platforms::Kubernetes.
class KubernetesService < DeploymentService
  include Gitlab::CurrentSettings
  include Gitlab::Kubernetes
  include ReactiveCaching

  self.reactive_cache_key = ->(service) { [service.class.model_name.singular, service.project_id] }

  # Namespace defaults to the project path, but can be overridden in case that
  # is an invalid or inappropriate name
  prop_accessor :namespace

  #  Access to kubernetes is directly through the API
  prop_accessor :api_url

  # Bearer authentication
  # TODO:  user/password auth, client certificates
  prop_accessor :token

  # Provide a custom CA bundle for self-signed deployments
  prop_accessor :ca_pem

  with_options presence: true, if: :activated? do
    validates :api_url, url: true
    validates :token
  end

  before_validation :enforce_namespace_to_lower_case

  validate :deprecation_validation, unless: :template?
  validates :namespace,
    allow_blank: true,
    length: 1..63,
    if: :activated?,
    format: {
      with: Gitlab::Regex.kubernetes_namespace_regex,
      message: Gitlab::Regex.kubernetes_namespace_regex_message
    }

  after_save :clear_reactive_cache!

  def initialize_properties
    self.properties = {} if properties.nil?
  end

  def title
    'Kubernetes'
  end

  def description
    'Kubernetes / Openshift integration'
  end

  def help
    'To enable terminal access to Kubernetes environments, label your ' \
    'deployments with `app=$CI_ENVIRONMENT_SLUG`'
  end

  def self.to_param
    'kubernetes'
  end

  def fields
    [
        { type: 'text',
          name: 'api_url',
          title: 'API URL',
          placeholder: 'Kubernetes API URL, like https://kube.example.com/' },
        { type: 'textarea',
          name: 'ca_pem',
          title: 'CA Certificate',
          placeholder: 'Certificate Authority bundle (PEM format)' },
        { type: 'text',
          name: 'namespace',
          title: 'Project namespace (optional/unique)',
          placeholder: namespace_placeholder },
        { type: 'text',
          name: 'token',
          title: 'Token',
          placeholder: 'Service token' }
    ]
  end

  def actual_namespace
    if namespace.present?
      namespace
    else
      default_namespace
    end
  end

  # Check we can connect to the Kubernetes API
  def test(*args)
    kubeclient = build_kubeclient!

    kubeclient.discover
    { success: kubeclient.discovered, result: "Checked API discovery endpoint" }
  rescue => err
    { success: false, result: err }
  end

  def predefined_variables
    config = YAML.dump(kubeconfig)

    variables = [
      { key: 'KUBE_URL', value: api_url, public: true },
      { key: 'KUBE_TOKEN', value: token, public: false },
      { key: 'KUBE_NAMESPACE', value: actual_namespace, public: true },
      { key: 'KUBECONFIG', value: config, public: false, file: true }
    ]

    if ca_pem.present?
      variables << { key: 'KUBE_CA_PEM', value: ca_pem, public: true }
      variables << { key: 'KUBE_CA_PEM_FILE', value: ca_pem, public: true, file: true }
    end

    variables
  end

  # Constructs a list of terminals from the reactive cache
  #
  # Returns nil if the cache is empty, in which case you should try again a
  # short time later
  def terminals(environment)
    with_reactive_cache do |data|
      pods = filter_by_label(data[:pods], app: environment.slug)
      terminals = pods.flat_map { |pod| terminals_for_pod(api_url, actual_namespace, pod) }
      terminals.each { |terminal| add_terminal_auth(terminal, terminal_auth) }
    end
  end

  # Caches resources in the namespace so other calls don't need to block on
  # network access
  def calculate_reactive_cache
    return unless active? && project && !project.pending_delete?

    # We may want to cache extra things in the future
    { pods: read_pods }
  end

  def kubeclient
    @kubeclient ||= build_kubeclient!
  end

  def deprecated?
    !active
  end

  def deprecation_message
    content = <<-MESSAGE.strip_heredoc
    Kubernetes service integration has been deprecated. #{deprecated_message_content} your clusters using the new <a href=\'#{Gitlab::Routing.url_helpers.project_clusters_path(project)}'/>Clusters</a> page
      MESSAGE
    content.html_safe
  end

  TEMPLATE_PLACEHOLDER = 'Kubernetes namespace'.freeze

  private

  def kubeconfig
    to_kubeconfig(
      url: api_url,
      namespace: actual_namespace,
      token: token,
      ca_pem: ca_pem)
  end

  def namespace_placeholder
    default_namespace || TEMPLATE_PLACEHOLDER
  end

  def default_namespace
    return unless project

    slug = "#{project.path}-#{project.id}".downcase
    slug.gsub(/[^-a-z0-9]/, '-').gsub(/^-+/, '')
  end

  def build_kubeclient!(api_path: 'api', api_version: 'v1')
    raise "Incomplete settings" unless api_url && actual_namespace && token

    ::Kubeclient::Client.new(
      join_api_url(api_path),
      api_version,
      auth_options: kubeclient_auth_options,
      ssl_options: kubeclient_ssl_options,
      http_proxy_uri: ENV['http_proxy']
    )
  end

  # Returns a hash of all pods in the namespace
  def read_pods
    kubeclient = build_kubeclient!

    kubeclient.get_pods(namespace: actual_namespace).as_json
  rescue KubeException => err
    raise err unless err.error_code == 404

    []
  end

  def kubeclient_ssl_options
    opts = { verify_ssl: OpenSSL::SSL::VERIFY_PEER }

    if ca_pem.present?
      opts[:cert_store] = OpenSSL::X509::Store.new
      opts[:cert_store].add_cert(OpenSSL::X509::Certificate.new(ca_pem))
    end

    opts
  end

  def kubeclient_auth_options
    { bearer_token: token }
  end

  def join_api_url(api_path)
    url = URI.parse(api_url)
    prefix = url.path.sub(%r{/+\z}, '')

    url.path = [prefix, api_path].join("/")

    url.to_s
  end

  def terminal_auth
    {
      token: token,
      ca_pem: ca_pem,
      max_session_time: current_application_settings.terminal_max_session_time
    }
  end

  def enforce_namespace_to_lower_case
    self.namespace = self.namespace&.downcase
  end

  def deprecation_validation
    return if active_changed?(from: true, to: false)

    if deprecated?
      errors[:base] << deprecation_message
    end
  end

  def deprecated_message_content
    if active?
      "Your cluster information on this page is still editable, but you are advised to disable and reconfigure"
    else
      "Fields on this page are now uneditable, you can configure"
    end
  end
end
